ALCOHOLS PRODUCTION FROM COMPLEX CARBON SOURCES IN TWO STRAINS OF Thermoanaerobacterium thermosaccharolyticum.

M. JULIA PETTINARI; EGOBURO DIEGO EZEQUIEL; DIAZ PEÑA ROCIO

San Miguel de Tucuman

Congreso; XII Congreso de Microbiologia General; 2017

SAMIGE

Fossil fuels generate large amounts CO2, emissions and toxic byproducts, and are obtained from non-renewable resources. In this context, biofuels represent an eco-friendly and sustainable alternative, and those obtained from lignocellulosic biomass are of special interest because they can be obtained from otherwise wasted agricultural crop residues.Degradation of lignocellulosic biomass and xylan was described in many organisms including bacteria belonging to the Clostridium genus. In this work we analyzed degradation of xylan and lignocellulosic biomass (sugarcane agricultural residue) by two strains of the related genus Thermoanaerobacterium Thermoanaerobacterium thermosaccharolyticum GCU5 isolated in our laboratory and the collection strain T. thermosaccharolyticum DSM 531. These strains are anaerobic thermophilic butanol and ethanol producers. The sugarcane agricultural residue used consists mainly of three polymers: cellulose (34,2%), hemicellulose (24,1%) and lignin (18,5%) along with smaller amounts of, extractives (8,8%) and ash (13,6%). Also, the heteropolymer xylan represents the most abundant hemicellulosic polysaccharide.To identify genes encoding the key enzymes in xylan degradation we performed a genomic analysis using RAST annotation Server, Blast algorithm and Biocyc database collection. Five enzymes were identified in both strains: Endo-1,4-β Xylanase (EC 3.2.1.8), β-Xylosidase (EC 3.2.1.37), α-N-Arabinofuranosidase 2 (EC 3.2.1.55) and Acetyl Xylan esterase (EC 3.1.1.72). We also searched the genomes of both strains for genes coding for enzymes involved in the degradation of cellulose. We identified genes encoding for β-glucosidase (EC 3.2.1.21), 1,3 β-Cellobiosidae (3.2.1.91) and putative Endo-1,4-β-D-Glucanase.Given that these strains carry the genes responsible for xylan and cellulose degradation, we decided to evaluate their ability to grow on these substrates. The strains were grown at 60°C in TSD medium supplemented with xylan or sugarcane agricultural residue as only carbon sources, using the Hungate method. After 48 hours we observed that GCU5 and DSZ 531 were able to grow in both carbon sources.Finally, we measured ethanol and butanol production by Head Space GC-FID. For this, the culture supernatants were diluted ½ in K2CO3 1g/ml, heated at 60°C for 1h and analyzed in a GC-FID. Although both strains were able to produce ethanol on TSD xylan and TSD sugarcane biomass, the production was higher by the strain T. thermosaccharolyticum DSM 531.In conclusion, we could demonstrate that two strains of T. thermosaccharolyticum are able to grow and produce solvents from complex substrates such as xylan and lignocellulosic biomass. These results are interesting for the development of biofuels, and especially relevant for our country, because sugarcane biomass is an economic substrate that is generated as a contaminating residue during sugarcane harvest.